Juri and her two brothers are amazed when a magical girl named Hinaki flies into their bedroom, supposedly in pursuit of her rebellious shadow. She and her fairy friend, Milkbell, come from a far-off place called Prism, where children stay perpetually young. Enchanted, the kids follow her back. But when Hinaki's nemesis, the pirate Rin Kurosawa causes trouble, the kids begin to miss their old life.